Region Code and DVD
Commercial DVDs are typically encoded for the region that they were released in. This is how producers maintain control over their copyright in international markets. This is a problem for foreign language teachers since they frequently buy a DVD in a foreign country and when they get home they are unable to use it. There are however, "Region-Free" DVD players which allow one to play any region coded DVD. Look on the packaging for "Region 0" or "All Region."
"Code-free" DVD
DVDs can also be coded for regional video output standards (PAL SECAM or NTSC). If the picture scrolls or "flips," then you probably have a DVD that expects to be played on a PAL standard TV or DVD player. Some DVD players are able to translate PAL and NTSC output to NTSC (US) televisions, and some cannot.